The invention relates to a radar apparatus, provided with an antenna, a transmitting and receiving unit coupled to the antenna, whereby the receiving unit is provided with a broadband preamplifier stage, to which signals, received with the aid of the antenna are applied, and with a bandwidth-limiting element coupled to it, the radar apparatus being furthermore provided with a jamming indicator, coupled to an output of the receiving unit, which indicator is suitable for detecting at least a part of the interference signals, detected with the aid of the antenna and the receiving unit and which for this purpose generates an interference signal-representing indication signal.
The invention also relates to a receiver device provided with a similar jamming indicator.
Radar equipment, provided with jamming indicators, capable of determining the direction and the strength of signals from jamming sources, are known from the technical literature, for instance "Introduction to Radar Systems" by M. I. Skolnik and are described in the chapter "Electronic Counter-Counter Measures". Said jamming indicators aim at detecting interference signals, containing frequency components, which are substantially equal to the frequency of the transmitting unit. These frequency components can penetrate the entire receiving unit. In this respect, a substantial class of interference signals is overlooked, in particular signals, whose frequencies lie within the bandwidth of the preamplifier stage of the receiving unit, but differ possibly intentionally from the frequency of the transmitting unit. These signals cannot penetrate the receiving unit and cannot be detected with state-of-the-art jamming indicators. Providing they are of sufficient strength, these signals can saturate the preamplifier stage of the receiving unit, thus rendering the radar apparatus insensitive to incoming target echoes. It is even possible that an object emitting interference signals of the above-mentioned type, can approach the radar without being detected. The invention has for its object to provide a solution to this problem.